This invention relates to a method for removal of trace mercury from industrial waste water and more particularly to a process for removing trace mercury from clinical and hospital waste water.
Waste water produced by hospitals and hospital-related industries originates from many sources. Such waste water is produced by clinical laboratories, research laboratories, medical waste incinerators equipped with fume scrubbers and hospital laundries.
Extremely complex and diverse waste waters are generated from a typical clinical/research laboratory associated with a hospital. They could contain ionic mercury and organic mercuric compounds (Methyl mercury and /or Thimersol an organic mercury compound used as a fixative for tissue specimens), other heavy metals, organic chemicals, blood products, body fluids, formaldehyde, dilute acids/bases, oxidizers, oil, grease, phosphates, detergents, wastes from automated instrumentation, photographic imaging chemicals, radionuclides and particulate matter. In addition they contain a variety of bacterial flora including pathogens from humans. The liquid waste stream from an incinerator scrubber usually has low concentrations of organic material but contains significant concentrations of heavy metals including mercury and particulate matter. Typical mercury concentrations range from 2 ppb to several hundred ppb. Such waste water volumes are anywhere from a few hundred gallons/day to over 50,000 gallons/day depending on the size of the institution. Currently these are discharged without any pretreatment other than pH adjustment.
Several state and federal agencies enforce a limit of 1 .mu.g/L (ppb) for the mercury in the discharge from these facilities. However compliance has been difficult due to the challenge of treating the mercury for such complex waste waters and the lack of a cost effective and reliable technology. The US Environmental Protection Agency has been focusing increased scrutiny on the impact of mercury discharges into the environment. Mercury is a bio-accumulating toxic, that poses a threat to fish and the food chain, including human beings. It, therefore, may not be discharged to ensure that the quality of the treated affluent and the bio-solids that are converted into fertilizer pellets, meet applicable state and federal regulatory limits.
It is therefore a principal object of the present invention to provide a method for removing mercury from waste water.
It is another object of the present invention to provide a method for removing mercury from waste water in a reliable and cost effective manner.